A novel approach to anterior segment imaging with smartphones in the COVID-19 era

Abstract

Purpose: To report a novel, telemedicine-friendly, smartphone-based, wireless anterior segment device with instant photo-documentation ability in the COVID-19 era.

Methods: Anterior Imaging Module (AIM) was constructed based on a 50/50 beam splitter design, to match the magnification drum optics of slit-lamps with a three-step or higher level of magnification. The design fills the smartphone sensor fully at the lowest magnification and matches the fixed focus of the slit-lamp. It comes with a smartphone for instant photo-documentation, an in-built software application for data-management and secure HIPAA compliant cloud storage, and a Bluetooth trigger for a one-tap image capture. The construction of the device is explained, and the optical resolution measured using U.S. air-force resolution test. AIM's performance was characterized with traceability to internationally relevant performance standards for digital slit-lamps after image quality assessment through a pilot study.

Results: Clinically useful anterior segment images were obtained with both diffuse and slit illumination at different magnification settings with the highest magnification (40X) resolution of 359 lines per cm and the lowest magnification (16X) resolution of 113 lines per cm.

Conclusion: AIM is a novel, wireless, telemedicine-enabled design that digitizes existing, analog slit lamps with at least three-step magnification. The settings ensure the focus is determined purely by the position of the slit-lamp. Hence, the image viewed and captured on the smartphone is exactly what the clinician sees through the eyepiece. This helps in maintaining distance from the patient in the ongoing COVID-19 pandemic, as well.

Keywords: Anterior segment imaging; COVID-19; conjunctiva; cornea; iris; lens; sclera; slit-lamp; smartphone; telemedicine; uniform illumination.

Figure 1

Optical Design of Anterior imaging Module (AIM)

Figure 2

(a) Hardware Design of Anterior imaging Module (AIM). (b) AIM mounted on a conventional slit-lamp. (c) Anterior segment imaging on AIM

Figure 3

(a) Anterior Segment image showing the plane of iris and lens in focus. (b) Anterior Segment image showing the plane of cornea in focus

Figure 4

(a) Diffuse illumination showing a congenital infero-nasal Coloboma (25X). (b) Optical section showing a clear lens (25X). (c) Diffuse illumination depicting a hyper mature sclerotic cataract with iris pigments on anterior lens surface (25X). (d) Retro illumination showing a well-centered capsulorhexis with single piece posterior chamber IOL in the capsular bag (16X). (e) Gonioscopy showing an open inferior angle up to ciliary body band with a possible neovascularization of the angle (25X). (f) Slit-lamp biomicroscopy with a 90D volk lens showing a healthy optic disc (25X)

Figure 5

AIM can effectively increase the physical distance between patient and examiner in the current COVID-19 pandemic

Figure 6

(a) Airforce Resolution Test for 6.5X (Row 1) and 10X magnification (Row 2). (b) Airforce Resolution Tests for 16X (Row 1) and 25X magnification (Row 2). (c) Airforce Resolution Tests for 40X magnification

Figure 7

(a) Conjunctival cyst in lower fornix (16X). (b) Upper tarsal conjunctiva showing a cobblestone appearance seen in giant papillary conjunctivitis (25X). (c) Granular corneal dystrophy showing discrete bread crumb-like opacities in the central anterior stroma of the cornea (40X). (d) Slit-image depicting a case of corneal hydrops following a break in Descemet’s membrane leading to corneal edema, managed with intracameral injection of air (25X). (e) Diffuse illumination showing a corneal scar with residual tattoo pigments (25X). (f) Slit illumination showing Post penetrating keratoplasty graft rejection (25X). (g) Indirect illumination under high magnification showing pigmented keratic precipitates on the corneal endothelium and ghost vessels (40X). (h) Emulsified silicone oil in the superior portion of the anterior chamber manifests as an “inverted hypopyon” or “hyperoleon” (25X)